Classification and preoperative radiographic evaluation: Knee

The failure of total knee arthroplasty (TKA) results in the presence of some degree of bone loss at the time of revision surgery. A classification system to describe the extent of bone loss assists the surgeon in planning the revision surgery. The Anderson Orthopaedic Research Institute (AORI) bone defect classification system includes three basic categories of bone loss and provides a basis for determining the need for stemmed components, augments, or bone grafts. Type 1 defects (intact metaphyseal bone) can be effectively managed by using primary components; Type 2 defects (damaged metaphyseal bone) are best managed with modular revision components; and Type 3 defects (deficient metaphyseal bone) require the lost bone to be reconstructed with structural bone graft(s), custom, or hinged components.